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Teach GVN that x+y is the same as y+x and that x<y is the same as y>x.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151365 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2012-02-24 15:16:31 +00:00
parent 8b93ff298c
commit e170c76ccd
2 changed files with 39 additions and 1 deletions
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17
lib/Transforms/Scalar/GVN.cpp
View File

@ -154,9 +154,24 @@ Expression ValueTable::create_expression(Instruction *I) {
for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
OI != OE; ++OI)
e.varargs.push_back(lookup_or_add(*OI));
if (I->isCommutative()) {
// Ensure that commutative instructions that only differ by a permutation
// of their operands get the same value number by sorting the operand value
// numbers. Since all commutative instructions have two operands it is more
// efficient to sort by hand rather than using, say, std::sort.
assert(I->getNumOperands() == 2 && "Unsupported commutative instruction!");
if (e.varargs[0] > e.varargs[1])
std::swap(e.varargs[0], e.varargs[1]);
}
if (CmpInst *C = dyn_cast<CmpInst>(I)) {
e.opcode = (C->getOpcode() << 8) | C->getPredicate();
// Sort the operand value numbers so x<y and y>x get the same value number.
CmpInst::Predicate Predicate = C->getPredicate();
if (e.varargs[0] > e.varargs[1]) {
std::swap(e.varargs[0], e.varargs[1]);
Predicate = CmpInst::getSwappedPredicate(Predicate);
}
e.opcode = (C->getOpcode() << 8) | Predicate;
} else if (InsertValueInst *E = dyn_cast<InsertValueInst>(I)) {
for (InsertValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end();
II != IE; ++II)

23
test/Transforms/GVN/commute.ll Normal file
View File

@ -0,0 +1,23 @@
; RUN: opt -gvn -S < %s | FileCheck %s
declare void @use(i32, i32)
define void @foo(i32 %x, i32 %y) {
; CHECK: @foo
%add1 = add i32 %x, %y
%add2 = add i32 %y, %x
call void @use(i32 %add1, i32 %add2)
; CHECK: @use(i32 %add1, i32 %add1)
ret void
}
declare void @vse(i1, i1)
define void @bar(i32 %x, i32 %y) {
; CHECK: @bar
%cmp1 = icmp ult i32 %x, %y
%cmp2 = icmp ugt i32 %y, %x
call void @vse(i1 %cmp1, i1 %cmp2)
; CHECK: @vse(i1 %cmp1, i1 %cmp1)
ret void
}